The invention relates to a method for constructing an electrical interconnection circuit for electronic components and to an apparatus for realising the method.
Miniaturised electronic components are generally fixed to an insulating base support on which are provided the various electrical interconnections between these components. In order to benefit to the maximum from the increasing miniaturisation of electronic components it is necessary to place a maximum number thereof on a minimum size base support surface. This result can only be obtained by miniaturising the electrical connections and by using insulated wires, whose installation can be carried out automatically and whose arrangement can be modified as required.
A certain number of methods and apparatuses are known making it possible to automatically produce in accordance with programmable arrangements the electrical interconnection circuits between different electronic components. However, these known apparatuses are generally complex in cases where they make it possible to obtain a suitable miniaturisation of the interconnection circuits. Simpler apparatuses do not make it possible to obtain a satisfactory component density, bearing in mind the miniaturisation thereof.
An apparatus is already known (see U.S. Pat. No. 4,031,612) in which an insulating base support is used incorporating conductive zones. The zones to be interconnected are linked by an insulating wire by adhering it to the base support and the bared wire is welded to the conductive zones and is cut after welding. This method has the advantage of the subsequent deposition of the interconnection wires making it possible to modify the interconnection circuit as required, on the basis of previously prepared standardised cards.
Moreover, another apparatus is known in which the electrical interconnection circuit is provided by means of a thermally weldable insulated wire which enables both a limitation in the dimensions of the interconnections permitting their crossings due to the insulation of the wire, whilst also making it possible to use an ancillary device for baring the wire, because the latter is bared and welded simultaneously by means of a welding iron. However, due to the double function of the iron and the linear contact between the latter and the wire to be welded, heating must last for a relatively long time in order to bring about the complete sublimation of the polyurethane varnish which normally forms the insulation surrounding the wire and the melting of the tin-lead layer deposited on the conductive pellet in order to bring about the weld. Thus, welding must be carried out on a relatively large conductive part (diameter approximately 2 mm) to ensure that the heating period has no prejudicial effects, such as separation and damage to the pellet. Thus, the overall dimensions of the interconnection circuit obtained with such an apparatus are not reduced sufficiently to permit an optimum utilisation of the presently available miniaturised electronic components. The apparatus is not therefore suitable for the automatic production of the electrical interconnection circuits between these components.